docs/DSP: Add sections on 16-bit and 40-bit modes and on main and extended opcode writing to the same register #10692
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docs/DSP/GameCube_DSP_Users_Manual/GameCube_DSP_Users_Manual.tex
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Note that there used to be a lot more inconsistencies with the opcode bits (see #10048, particularly 446b1d2). |
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Spawned off discussion in dolphin-emu#10692, this introduces a general document that can be used to document intentional divergences from hardware behavior (e.g. due to it being negligible, more practical, intensive to implement properly for most games, etc). For the initial introduction of the document, this only condenses the information from the originating discussion. Any other noteworthy differences can be later added by others.
Spawned off discussion in dolphin-emu#10692, this introduces a general document that can be used to document intentional divergences from hardware behavior (e.g. due to it being negligible, more practical, intensive to implement properly for most games, etc). For the initial introduction of the document, this only condenses the information from the originating discussion. Any other noteworthy differences can be later added by others.
$acS.h was a typo, which has been replaced with $acD.h.
…rite to the same register (the write backlog) For more information, ApplyWriteBackLog, WriteToBackLog, and ZeroWriteBackLog were added in b787f5f and the explanatory comment was added in fd40513, although it did not mention the specific instructions that could trigger this edge case. The statements about which registers can be written by main opcodes and extension opcodes are based on my own checking of all instructions in the manual.
…mediate These instructions used an 'r' in their bit list, but a 'd' in the operands.
We don't have anything called $amD, though we do have $acsD. However, these instructions affect flags based on the whole accumulator, so it's better to just use $acD.
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I've added hardware tests for the 40-bit mode (one testing a large range of values, though not all of them as that would take several days to run, and one testing various instructions), replaced the cryptic "Perform an additional operation depending on destination register" messages with a reference to the new 40-bit mode section, and also fixed a few more typos. The new version of the manual is here: GameCube_DSP_Users_Manual.pdf. |
The GFDL requires the history section to be updated.
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I discovered that |
Along with various typo fixes in both the DSP manual and comments in Dolphin's DSP code. The new sections are based on studying Dolphin's DSP interpreter, and not by hardware testing.
This is a draft because I am considering replacing the existing "Perform an additional operation depending on destination register." messages in various instructions with a more explicit back-reference to the "16-bit and 40-bit modes" subsection (along with adding it to any instructions where it's missing but exists in Dolphin), but haven't done so yet.